Mike,
At this time it is only JAWS that seems to support the scope
attribute. Other readers like Window-Eyes and NVDA do not.
Some time ago, even JAWS did not support rowspan and its use for
complex tables was not recommended. And then the support for scope in
JAWS had also gone awry. (I had filed a bug with Freedom Scientific
then). Now the support for scope is much better with JAWS.
See user agent notes for technique H63 for WCAG2 and the last
resource listed on that page.
Sailesh Panchang
Accessibility Services Lead
Deque Systemswww.deque.com